These are large in comparison with the other vertebrae.
The atlas and axis are usually fused into one bone and (including the atlas and
axis as two) there are usually 8 cervicals in the early pterosaurs, reducing to
6 in some of the later and the larger pterosaurs. The cervicals have a
thin outer layer of hard bone and a centre of cancellous (spongy) bone and
pneumatic cavities (air pockets). There are generally no cervical ribs.

Cervical vertebrae are the commonest form of vertebrae to be
found disassociated from other fossil remains. Their size depends upon the
species. Some specimens may be worn and lose their zygapophyses and neural
spines (sticky out bits).

Small Pterosaurs

The cervical vertebrae of the smaller pterosaurs like
Rhamphorhynchus and Pterodactylus are typical of many types of
Pterodactyl vertebrae. On the left are diagrams of the first four
cervicals of these two genera.

a - Atlas
ax - Axis
c3 - Third cervical
c4 - Fourth cervical

With its more solid skull, the Rhamphorhynchus needs sturdier cervical
vertebrae. The Pterodactylus vertebrae are longer and flatter.

Large Pterosaurs

Pteranodon is a large pterosaur with a completely fused atlo-axis vertebra articulating with the skull.

The cervical vertebrae in
this species are covered with a very thin periosteum (hard bone layer) and a
layer of cancellous bone (spongy bone). There are air cavities in the
bone and a pneumatic foramen can be seen in the centre of the lateral view
on these vertebra.

pn - Pneumatic foramen

Almost all of the bones of the spine in
Pteranodon were filled with air.

The Ornithosaurs are a widely varied group and
their cervical vertebrae differ from species to species. The
illustration shows a typical set of Ornithocheirid vertebrae, drawn from
specimens from the Cambridge Greensand.

These vertebrae, like most
Ornithocheirid cervicals show large pneumatic foramina. They are generally
quite flat and wide.

There are also a number of pterosaurs with very long cervical
vertebrae. Typical examples are the Azhdarchid like Azhdarcho,
Quetzalcoatlus and Arambourginiana. Such specimens are very rare.

To the right is a typical example of a
Pterodactyl fossil. This is Pterodactylus Kochi from the Lithographic
Limestone of Bavaria, Germany. The vertebrae of the neck are clearly
preserved and only slightly crushed.

The bones of Pterosaurs are thin
walled and fragile and they tend to become crushed in many deposits during
the fossilization process.

It can be seen that this specimen shows 6 cervical vertebrae, including
the atlas and axis. An impression of the area of the neck can also be
seen in this fossil.

Credits

The diagrams of Rhamphorhynchus and
Pterodactylus are drawn after the reconstructions of Peter Wellnhofer.

The diagram of Pteranodon is drawn
after the reconstruction of G. H. Eaton.

The diagram of Ornithocheirus is drawn
from fossils in the Yorkshire Museum collections.

The photograph of Pterodactylus Kochi is
taken from a cast in the Pursglove Collection.